(14) Light Sport Aircraft, Experimental Aircraft, EAB, LSA, ELSA - Explained. - YouTube

Long story short, if your building a custom airplane of your own design (meaning you are not just building a replica of the manufacturers SLSA as Kitfox offers) You are building a EAB. Keep it under 1320 lbs and you are legal to fly it as a Sport Pilot. Obviously that is not the only restriction. Watch the first 7 min of this video and you will understand.